//==========================================================================
// Copyright (c) 2000-2008,  Elastos, Inc.  All Rights Reserved.
//==========================================================================
/*  $KAME: uipc_mbuf2.c,v 1.31 2001/11/28 11:08:53 itojun Exp $ */
/*  $NetBSD: uipc_mbuf.c,v 1.40 1999/04/01 00:23:25 thorpej Exp $   */

/*
 * Copyright (C) 1999 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * Copyright (c) 1982, 1986, 1988, 1991, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *  This product includes software developed by the University of
 *  California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *  @(#)uipc_mbuf.c 8.4 (Berkeley) 2/14/95
 */
//#include <sys/netmisc.h>
//#include <sys/cdefs.h>
//__FBSDID("$FreeBSD: src/sys/kern/uipc_mbuf2.c,v 1.20 2003/06/11 00:56:58 obrien Exp $");

/*#define PULLDOWN_DEBUG*/

//#include "opt_mac.h"

//#include <sys/param.h>
//#include <sys/systm.h>
//#include <sys/kernel.h>
//#include <sys/lock.h>
//#include <sys/mac.h>
//#include <sys/malloc.h>
//#include <sys/mbuf.h>
//#include <sys/mutex.h>

#include "mbuf_.h"

//MALLOC_DEFINE(M_PACKET_TAGS, "tag", "packet-attached information");

/* can't call it m_dup(), as freebsd[34] uses m_dup() with different arg */
static struct mbuf *m_dup1(struct mbuf *, int, int, int);

/*
 * ensure that [off, off + len) is contiguous on the mbuf chain "m".
 * packet chain before "off" is kept untouched.
 * if offp == NULL, the target will start at <retval, 0> on resulting chain.
 * if offp != NULL, the target will start at <retval, *offp> on resulting chain.
 *
 * on error return (NULL return value), original "m" will be freed.
 *
 * XXX: M_TRAILINGSPACE/M_LEADINGSPACE only permitted on writable ext_buf.
 */
struct mbuf *
m_pulldown(struct mbuf *m, int off, int len, int *offp)
{
    struct mbuf *n, *o;
    int hlen, tlen, olen;
    int writable;

    /* check invalid arguments. */
    if (m == NULL)
        kprintf("error: m == NULL in m_pulldown()");
    if (len > MCLBYTES) {
        m_freem(m);
        return NULL;    /* impossible */
    }

#ifdef PULLDOWN_DEBUG
    {
    struct mbuf *t;
    printf("before:");
    for (t = m; t; t = t->m_next)
        printf(" %d", t->m_len);
    printf("\n");
    }
#endif
    n = m;
    while (n != NULL && off > 0) {
        if (n->m_len > off)
            break;
        off -= n->m_len;
        n = n->m_next;
    }
    /* be sure to point non-empty mbuf */
    while (n != NULL && n->m_len == 0)
        n = n->m_next;
    if (!n) {
        m_freem(m);
        return NULL;    /* mbuf chain too short */
    }

    /*
     * XXX: This code is flawed because it considers a "writable" mbuf
     *      data region to require all of the following:
     *    (i) mbuf _has_ to have M_EXT set; if it is just a regular
     *        mbuf, it is still not considered "writable."
     *    (ii) since mbuf has M_EXT, the ext_type _has_ to be
     *         EXT_CLUSTER. Anything else makes it non-writable.
     *    (iii) M_WRITABLE() must evaluate true.
     *      Ideally, the requirement should only be (iii).
     *
     * If we're writable, we're sure we're writable, because the ref. count
     * cannot increase from 1, as that would require posession of mbuf
     * n by someone else (which is impossible). However, if we're _not_
     * writable, we may eventually become writable )if the ref. count drops
     * to 1), but we'll fail to notice it unless we re-evaluate
     * M_WRITABLE(). For now, we only evaluate once at the beginning and
     * live with this.
     */
    /*
     * XXX: This is dumb. If we're just a regular mbuf with no M_EXT,
     *      then we're not "writable," according to this code.
     */
    writable = 0;
    if ((n->m_flags & M_EXT) == 0 ||
        (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
        writable = 1;

    /*
     * the target data is on <n, off>.
     * if we got enough data on the mbuf "n", we're done.
     */
    if ((off == 0 || offp) && len <= n->m_len - off && writable)
        goto ok;

    /*
     * when len <= n->m_len - off and off != 0, it is a special case.
     * len bytes from <n, off> sits in single mbuf, but the caller does
     * not like the starting position (off).
     * chop the current mbuf into two pieces, set off to 0.
     */
    if (len <= n->m_len - off) {
        o = m_dup1(n, off, n->m_len - off, M_DONTWAIT);
        if (o == NULL) {
            m_freem(m);
            return NULL;    /* ENOBUFS */
        }
        n->m_len = off;
        o->m_next = n->m_next;
        n->m_next = o;
        n = n->m_next;
        off = 0;
        goto ok;
    }

    /*
     * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
     * and construct contiguous mbuf with m_len == len.
     * note that hlen + tlen == len, and tlen > 0.
     */
    hlen = n->m_len - off;
    tlen = len - hlen;

    /*
     * ensure that we have enough trailing data on mbuf chain.
     * if not, we can do nothing about the chain.
     */
    olen = 0;
    for (o = n->m_next; o != NULL; o = o->m_next)
        olen += o->m_len;
    if (hlen + olen < len) {
        m_freem(m);
        return NULL;    /* mbuf chain too short */
    }

    /*
     * easy cases first.
     * we need to use m_copydata() to get data from <n->m_next, 0>.
     */
    if ((off == 0 || offp) && M_TRAILINGSPACE(n) >= tlen
     && writable) {
        m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
        n->m_len += tlen;
        m_adj(n->m_next, tlen);
        goto ok;
    }
    if ((off == 0 || offp) && M_LEADINGSPACE(n->m_next) >= hlen
     && writable) {
        n->m_next->m_data -= hlen;
        n->m_next->m_len += hlen;
        bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), hlen);
        n->m_len -= hlen;
        n = n->m_next;
        off = 0;
        goto ok;
    }

    /*
     * now, we need to do the hard way.  don't m_copy as there's no room
     * on both end.
     */
    MGET(o, M_DONTWAIT, m->m_type);
    if (o && len > MLEN) {
        MCLGET(o, M_DONTWAIT);
        if ((o->m_flags & M_EXT) == 0) {
            m_free(o);
            o = NULL;
        }
    }
    if (!o) {
        m_freem(m);
        return NULL;    /* ENOBUFS */
    }
    /* get hlen from <n, off> into <o, 0> */
    o->m_len = hlen;
    bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), hlen);
    n->m_len -= hlen;
    /* get tlen from <n->m_next, 0> into <o, hlen> */
    m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
    o->m_len += tlen;
    m_adj(n->m_next, tlen);
    o->m_next = n->m_next;
    n->m_next = o;
    n = o;
    off = 0;

ok:
#ifdef PULLDOWN_DEBUG
    {
    struct mbuf *t;
    printf("after:");
    for (t = m; t; t = t->m_next)
        printf("%c%d", t == n ? '*' : ' ', t->m_len);
    printf(" (off=%d)\n", off);
    }
#endif
    if (offp)
        *offp = off;
    return n;
}

static struct mbuf *
m_dup1(struct mbuf *m, int off, int len, int wait)
{
    struct mbuf *n;
    int l;
    int copyhdr;

    if (len > MCLBYTES)
        return NULL;
    if (off == 0 && (m->m_flags & M_PKTHDR) != 0) {
        copyhdr = 1;
        MGETHDR(n, wait, m->m_type);
        l = MHLEN;
    } else {
        copyhdr = 0;
        MGET(n, wait, m->m_type);
        l = MLEN;
    }
    if (n && len > l) {
        MCLGET(n, wait);
        if ((n->m_flags & M_EXT) == 0) {
            m_free(n);
            n = NULL;
        }
    }
    if (!n)
        return NULL;

    if (copyhdr && !m_dup_pkthdr(n, m, wait)) {
        m_free(n);
        return NULL;
    }
    m_copydata(m, off, len, mtod(n, caddr_t));
    return n;
}

/* Get a packet tag structure along with specified data following. */
struct m_tag *
m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
{
    struct m_tag *t;

    if (len < 0)
        return NULL;
    MALLOC(t, struct m_tag*, len + sizeof(struct m_tag), /*M_PACKET_TAGS*/0, wait);
    if (t == NULL)
        return NULL;
    t->m_tag_id = type;
    t->m_tag_len = len;
    t->m_tag_cookie = cookie;
    return t;
}

/* Free a packet tag. */
void
m_tag_free(struct m_tag *t)
{
#ifdef MAC
    if (t->m_tag_id == PACKET_TAG_MACLABEL)
        mac_destroy_mbuf_tag(t);
#endif
    FREE(t, /*M_PACKET_TAGS*/0);
}

/* Prepend a packet tag. */
void
m_tag_prepend(struct mbuf *m, struct m_tag *t)
{
    KASSERT(m && t, ("m_tag_prepend: null argument, m %p t %p", m, t));
    SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
}

/* Unlink a packet tag. */
void
m_tag_unlink(struct mbuf *m, struct m_tag *t)
{
    KASSERT(m && t, ("m_tag_unlink: null argument, m %p t %p", m, t));
    SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
}

/* Unlink and free a packet tag. */
void
m_tag_delete(struct mbuf *m, struct m_tag *t)
{
    KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));
    m_tag_unlink(m, t);
    m_tag_free(t);
}

/* Unlink and free a packet tag chain, starting from given tag. */
void
m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
{
    struct m_tag *p, *q;

    KASSERT(m, ("m_tag_delete_chain: null mbuf"));
    if (t != NULL)
        p = t;
    else
        p = SLIST_FIRST(&m->m_pkthdr.tags);
    if (p == NULL)
        return;
    while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
        m_tag_delete(m, q);
    m_tag_delete(m, p);
}

/* Find a tag, starting from a given position. */
struct m_tag *
m_tag_locate(struct mbuf *m, u_int32_t cookie, int type, struct m_tag *t)
{
    struct m_tag *p;

    KASSERT(m, ("m_tag_locate: null mbuf"));
    if (t == NULL)
        p = SLIST_FIRST(&m->m_pkthdr.tags);
    else
        p = SLIST_NEXT(t, m_tag_link);
    while (p != NULL) {
        if (p->m_tag_cookie == cookie && p->m_tag_id == type)
            return p;
        p = SLIST_NEXT(p, m_tag_link);
    }
    return NULL;
}

/* Copy a single tag. */
struct m_tag *
m_tag_copy(struct m_tag *t, int how)
{
    struct m_tag *p;

    KASSERT(t, ("m_tag_copy: null tag"));
    p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, how);
    if (p == NULL)
        return (NULL);
#ifdef MAC
    /*
     * XXXMAC: we should probably pass off the initialization, and
     * copying here?  can we hide that PACKET_TAG_MACLABEL is
     * special from the mbuf code?
     */
    if (t->m_tag_id == PACKET_TAG_MACLABEL) {
        if (mac_init_mbuf_tag(p, how) != 0) {
            m_tag_free(p);
            return (NULL);
        }
        mac_copy_mbuf_tag(t, p);
    } else
#endif
        bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
    return p;
}

/*
 * Copy two tag chains. The destination mbuf (to) loses any attached
 * tags even if the operation fails. This should not be a problem, as
 * m_tag_copy_chain() is typically called with a newly-allocated
 * destination mbuf.
 */
int
m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
{
    struct m_tag *p, *t, *tprev = NULL;

    KASSERT(to && from,
        ("m_tag_copy_chain: null argument, to %p from %p", to, from));
    m_tag_delete_chain(to, NULL);
    SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
        t = m_tag_copy(p, how);
        if (t == NULL) {
            m_tag_delete_chain(to, NULL);
            return 0;
        }
        if (tprev == NULL)
            SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
        else
            SLIST_INSERT_AFTER(tprev, t, m_tag_link);
        tprev = t;
    }
    return 1;
}

/* Initialize tags on an mbuf. */
void
m_tag_init(struct mbuf *m)
{
    SLIST_INIT(&m->m_pkthdr.tags);
}

/* Get first tag in chain. */
struct m_tag *
m_tag_first(struct mbuf *m)
{
    return SLIST_FIRST(&m->m_pkthdr.tags);
}

/* Get next tag in chain. */
struct m_tag *
m_tag_next(struct mbuf *m, struct m_tag *t)
{
    return SLIST_NEXT(t, m_tag_link);
}
